Deposition Chamber Cleaning System and Method

ABSTRACT

An in-situ method of cleaning a vacuum deposition chamber can include flowing at least one reactive gas into the chamber.

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/312,083, filed on Mar. 9, 2010, which is incorporated byreference in its entirety.

TECHNICAL FIELD

This invention relates to a system and method of cleaning a depositionchamber.

BACKGROUND

Deposition methods can result in film growth not only covering thesubstrate to be coated, but also the reaction chamber walls and shields.For example, a first precursor can form a layer on a deposition chambersurface and can react with a second precursor to form a layer of amaterial on a deposition chamber surface. This, in turn, can lead tobuild up of deposits on the chamber walls and shields over time.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic depicting the gas pulse sequence of amanufacturing process.

FIG. 2 is a flowchart depicting the steps of a method for cleaning adeposition chamber.

FIG. 3 is a schematic depicting the gas pulse sequence of amanufacturing process.

FIG. 4 is a schematic depicting the gas pulse sequence of amanufacturing process.

FIG. 5 is a schematic depicting the gas pulse sequence of amanufacturing process.

FIG. 6 is a schematic depicting the gas pulse sequence of amanufacturing process.

FIG. 7 is a schematic depicting a deposition system.

DETAILED DESCRIPTION

Atomic layer deposition (ALD) is a thin film deposition technique thatis based on the sequential use of a gas phase chemical process. By usingALD, film thickness depends only on the number of reaction cycles, whichmakes the thickness control accurate and simple. Unlike chemical vapordeposition (CVD), there is less need of reactant flux homogeneity, whichgives large area (large batch and easy scale-up) capability, excellentconformality and reproducibility, and simplifies the use of solidprecursors.

Manufacturing a semiconductor device can include a thin film depositionprocess. Many deposition methods inadvertently result in film growth notonly covering the substrate to be coated, but also the reaction chamberwalls and shields. For example, in an atomic layer deposition orchemical vapor deposition, all surfaces suitable to allow for adsorptionof the first precursor and providing conditions to allow the chemicalreaction to occur with the second precursor. This can inadvertentlyresult in film growth not only covering the substrate to be coated, butalso the reaction chamber walls and shields. At some point depositionbuild up on the walls and shields reaches a critical thickness wherefilm stress results in delamination. The ensuing flaking particles aretypically undesirable and impact the film to be grown on the substrate.Thus, the walls and shields need to be cleaned periodically.

Cleaning is typically done by removing the shields and cleaning themeither mechanically (e.g. bead blasting, brushing) or through chemicalimmersion. These cleaning procedures can adversely affect a reduction inequipment availability (uptime). In order for a deposition process to bean economically viable process in volume manufacturing applications, itis desirable to minimize equipment downtime associated with cleaning.One approach to minimizing cleaning downtime is to simplify the processof removing and replacing shields. These fast-change shields can beeffective in reducing preventative maintenance down time. However,further improvement is required for cost effective deposition process,particularly in cost sensitive applications. A new method and system aredeveloped to address cleaning deposition chamber surfaces coated withdeposition materials.

An in-situ deposition chamber cleaning method can be used to remove thedeposit build-up by deposition processes such as ALD and CVD. Examples,of films formed by such deposition processes can include metalchalcogenides. Examples of metal chalcogenides formed on depositionchamber surfaces include aluminum oxide (Al₂O₃), aluminum sulfide(Al₂S₃), aluminum selenide (Al₂Se₃) (or combinations thereof), indiumoxide (In₂O₃), indium sulfide (In₂S₃), indium selenide (In₂Se₃) (orcombinations thereof), or zinc oxide (ZnO), zinc sulfide (ZnS), or zincselenide (ZnSe) (or combinations thereof), or titanium oxide (TiO₂),titanium sulfide (TiS₂), or titanium selenide (TiSe₂) (or combinationsthereof). The in-situ cleaning method can clean the chamber wall andshield, without removal of the shields from the reactor. A goal of thisin-situ cleaning method is to provide for more frequent cleaning cyclesthereby reducing the particle generation and associated yield andprocess performance problems. Another goal of this alternate cleaningmethod is to improve deposition tool availability by providing a fastchamber cleaning method that does not require tool downtime.Specifically, it can clean the chamber chemically in-situ rather thanmechanically or chemically ex-situ. In some embodiments, a reactive gas,such as gas phase hydrogen chloride (HCl), can be flown through thereactor. The reactive gas can include any suitable gas that can reactwith the deposits on the chamber walls and shields in such a way as toremove the deposited film.

In one aspect, a method of cleaning a deposition chamber can includepulsing a reactive gas including a hydrogen halide into a depositionchamber containing a metal chalcogenide formed on a deposition chambersurface to form a purgable material. The method can include purging thepurgable material from the deposition chamber.

The purgable material can include forming a vapor. The purgable materialcan include a particulate. The hydrogen halide can include hydrogenchloride, hydrogen bromide, hydrogen iodide, or hydrogen fluoride.Purging the purgable material from the deposition chamber can includepulsing an inert gas into the deposition chamber to flush the purgablematerial out of the chamber. The method can include heating thedeposition chamber to maintain the purgable vapor material as a vapor.The method can include introducing a chemically reactive plasma into thedeposition chamber to react with metal chalcogenide.

The method can include pulsing a second reactive gas into the depositionchamber after pulsing the reactive gas into the deposition chamber. Thesecond reactive gas can include oxygen. The second reactive gas caninclude an acid. The second reactive gas can include fluorine. Thesecond reactive gas can include tetrafluoromethane.

As mentioned above, purging the purgable material from the depositionchamber can include pulsing an inert gas into the deposition chamber.The inert gas can include helium. The inert gas can include nitrogen.

In another aspect, a method of manufacturing a semiconductor device caninclude transporting a substrate into a deposition chamber and forming abuffer layer adjacent to the substrate. Forming the buffer layer caninclude pulsing at least one metal precursor and pulsing at least onechalcogen precursor into the chamber. The method can includetransporting the substrate with the deposited buffer layer out of thechamber. The method can include pulsing a reactive gas including ahydrogen halide into the deposition chamber to react with a metalchalcogenide formed on a deposition chamber surface to form a purgablematerial. The method can include purging the purgable material from thedeposition chamber. The method can include purging the chalcogenprecursor before pulsing the reactive gas into the deposition chamber.

The purgable material can include a vapor. The purgable material caninclude a particulate. The hydrogen halide can include hydrogenchloride, hydrogen bromide, hydrogen iodide, or hydrogen fluoride.Purging the purgable material from the deposition chamber can includepulsing an inert gas into the deposition chamber to flush the purgablematerial out of the chamber. The method can include heating thedeposition chamber to maintain the purgable vapor material as a vapor.The method can include forming a chemically reactive plasma in thedeposition chamber to react with metal chalcogenide.

The method can include pulsing a second reactive gas into the depositionchamber after pulsing the reactive gas. The second reactive gas caninclude an acid, oxygen, fluorine, or tetrafluoromethane. As mentionedabove, purging the purgable material from the deposition chamber caninclude pulsing an inert gas into the deposition chamber. The inert gascan include helium or nitrogen. The method can include heating thesubstrate before pulsing a precursor. The semiconductor device caninclude a photovoltaic device.

In another aspect, a system for cleaning a metal chalcogenide residuefrom a deposition chamber surface can include a deposition chamberincluding an interior surface, a deposition gas inlet, a reactive gasinlet, an inert gas inlet, and an outlet. The system can include areactive gas source connected to the reactive gas inlet and configuredto deliver a reactive gas including a hydrogen halide to the depositionchamber, where the reactive gas can react with a metal chalcogenideformed on the interior surface to form a purgable material. The systemcan include an inert gas source connected to the inert gas inlet andconfigured to deliver an inert gas to the deposition chamber and flush apurgable material from the deposition chamber through the outlet.

The metal chalcogenide can include aluminum, indium, zinc, or titanium.The metal chalcogenide can include oxygen, sulfur, or selenium. Thehydrogen halide can include hydrogen chloride, hydrogen bromide,hydrogen iodide, or hydrogen fluoride. The system can include a secondreactive gas source including an acid, oxygen, fluorine, ortetrafluoromethane. The inert gas source can include nitrogen or helium.The system can include heater to heat the deposition chamber interiorsurface to a temperature sufficient to maintain a purgable material as avapor.

Referring to FIG. 1, a typical cycle of in-situ clean process caninclude two pulses of gas: a pulse of reactive gas (cleaning) and apulse of inert gas (purging).

As shown below, a reactive gas (RG in FIG. 1), such as gas phasehydrogen chloride (HCl), can be pulsed into the deposition chamber toreact with and remove the metal chalcogenide deposit:

Al₂X_(3(s))+6HCl_((g))->2AlCl_(3(s))+3H₂X_((g)) (X═O, S, or Se)

In₂X_(3(s))+6HCl_((g))->2InCl_(3(s)+)3H₂X_((g)) (X═O, S, or Se)

ZnX_((s))+2HCl_((g))->ZnCl_(2(s))+H₂X_((g)) (X═O, S, or Se)

The reactant from such a reaction can be a solid. Hence, in someembodiments, the cleaning temperature and gas can be selected to assurethat the resulting solid will have a vapor pressure high enough to be inthe gas phase. Indium chloride (e.g., InCl₃), for example, sublimes atapproximately 300° C. while its melting point is 586° C. Alternatively,in other embodiments, the particles can be small enough to be flushedthrough with the purging inert gas (IG in FIG. 1) before the nextdeposition cycle. This can be achieved not only by the temperature, butalso the concentration of the cleaning gas. Dilution of the cleaning gascan be the applicable variable. The frequency and duration of thecleaning cycles can be adjusted to the deposition process andsensitivity to particles. Furthermore, following the cleaning gasinjection the purge duration can be adjusted to assure that all of thecleaning gas has been flushed from the reaction chamber.

In some embodiments, the cleaning process can include a reactive ionetch (RIE) process. Reactive ion etching (RIE) is an etching technologywidely used in microfabrication. It can use chemically reactive plasmato remove material deposited on chamber walls and shields. The plasmacan be generated under low pressure (vacuum) by an electromagneticfield. High-energy ions from the plasma can attack the deposit build-upon the surface and react with it.

The in-situ cleaning method can include any suitable dry etch techniqueand process. The in-situ cleaning method can include providingchemically reactive plasma to facilitate removing of the depositedresidue. The reactive gas can include oxygen, hydrogen, chlorine, orfluorine. The reactive gas can include tetrafluoromethane.

Thin film deposition is widely used in semiconductor devicemanufacturing, such as photovoltaic device manufacturing. Photovoltaicdevices can include multiple layers formed on a substrate (orsuperstrate). For example, a photovoltaic device can include aconducting layer, a semiconductor absorber layer, a buffer layer, asemiconductor window layer, and a transparent conductive oxide (TCO)layer, formed in a stack on a substrate. Each layer may in turn includemore than one layer or film. Each layer can cover all or a portion ofthe device and/or all or a portion of the layer or substrate underlyingthe layer. For example, a “layer” can mean any amount of any materialthat contacts all or a portion of a surface. As a result, themanufacturing process can include a plurality of thin film depositionprocess. The in-situ cleaning process can be implemented as often asevery deposition cycle. It is more likely that cleaning would beperformed periodically after some total deposition time (or thickness)as determined by process and uptime optimization for a given depositionchemistry and process.

Advantageously, in this in-situ cleaning method, the chamber temperaturecan be maintained at or near process temperatures during the cleaning,thereby eliminating the time that it takes for the system to cool andthen re-heat as a result of normal ex-situ cleaning. Another feature ofthis in-situ cleaning method is that the chamber environment does notneed to be opened to air and subsequently purged of airborne processcontaminants such as unwanted oxygen, carbon, water vapor, hydrocarbonsand etc.

Referring to FIG. 2, an in-situ method for cleaning a deposition chambercan include the steps of: 1) pulsing a reactive gas in a depositionchamber; 2) reacting the reactive gas with the deposit build-up; 3)purging the chamber with an inert gas.

Referring to FIG. 3, an in-situ cleaning cycle can follow an ALDdeposition cycle. For example, metal precursor gas flow (PG1) can beintroduced into the chamber, and adsorb and react with the surface. Thedose of the metal precursor gas can be adjusted to obtain surfacesaturation, i.e. all available processing surface sites can be used forreaction with the precursor. When it is obtained, the precursor inletcan be closed and the chamber purged with inert gas (IG) leaving onlythe layer of reacted species on the processing surface. Chalcogenprecursor (PG2) is then introduced and react with the first layerforming a monolayer of the desired material (e.g. a metal chalcogenidefor a buffer layer) while the byproducts desorb and are pumped out. Thechamber can be purged again with inert gas (IG). This pulsing sequencecorresponds to one ALD cycle. The sequence can be repeated up to adesired or predetermined number of cycles and the thickness can becontrolled on a monolayer level. The substrate with the deposited filmcan then be transported from the chamber. If the substrate remains inthe deposition chamber, the reactive gas pulsed into the depositionchamber can react with the metal chalcogenide layer formed thereon andcan remove the intended metal chalcogenide layer. Therefore, thesubstrate can be removed before the reactive gas is pulsed.

When the reactive gas (RG), such as gas phase hydrogen chloride (HCl),is pulsed, it can be flowed through the reactor to react with and removethe metal chalcogenide deposit on the chamber walls and shields. Theresulting particles can be small enough to be flushed through with thepurging inert gas (IG) before the next deposition cycle. The in-situcleaning cycle can be repeated till the existence of deposit residue inthe chamber is reduced to a level that will not negatively effect thefollowing deposition cycle. The reactive gas step can be repeatedbetween each substrate, or between multiples of substrates on which ametal chalcogenide layer is deposited. For example, the reactive gasstep can be carried out once for every two to five substrates treated.The reactive gas step can be carried out once for every 5 to 10substrates treated. The reactive gas step can be carried out at anysuitable interval to achieve the optimal balance of deposition chambercondition and down-time. Down-time can be minimized by maximizing thenumber of substrates processed between each reactive gas treatment. Thenumber of substrates processed between each reactive gas treatment canbe increased to minimize down-time. For example, the reactive gas stepcan be carried out as infrequently as once for every 2,000 or fewer(e.g., about 1,000) substrates.

The reactive gas can include any suitable gas. For example, the reactivegas can include a hydrogen halide, such as hydrogen chloride. Thereactive gas can be diluted with any suitable gas such as an inert gas.Examples of inert gases that can be used to dilute the reactive gas caninclude helium and nitrogen. The reactive gas can be diluted with anyother suitable gas, including a second reactive gas.

Referring to FIG. 4, an in-situ cleaning cycle can follow a depositioncycle, such as a CVD deposition cycle. For example, at least twoprecursor gas flow (PG1 and PG2) can be introduced into the chamber,react and/or decompose on the substrate surface to produce the desireddeposit. When the deposition is done, the precursor inlet can be closedand the chamber purged with inert gas (IG) displacing the precursor gasfrom the chamber. This pulsing sequence corresponds to one CVD cycle.The sequence can be repeated up to a desired or predetermined number ofcycles and the thickness can be controlled on a monolayer level. Thesubstrate with the deposited film can then be transported from thechamber.

After that, reactive gas (RG), such as gas phase hydrogen chloride(HCl), can be flown through the reactor to react with and remove thedeposit. The resulting particles can be small enough to be flushedthrough with the purging inert gas (IG) before the next depositioncycle. The in-situ cleaning cycle can be repeated till the existence ofdeposit residue in the chamber is reduced to a level that will notnegatively effect the following deposition cycle.

Referring to FIGS. 5 and 6, more than one reactive gas (RG1 and RG2) canbe introduced to the chamber for in-situ cleaning process. For example,depending on the deposit residue need to be removed, the reactive gascan include a combination of gas phase etchants, such as CF₄/O₂, SF₆/O₂,or BCl₃/Cl₂. The in-situ cleaning method can also be used to clean thedeposit build-up by any other applicable deposition process, such asevaporation or sputtering.

Referring to FIG. 7, deposition system 100 can include apparatus forcleaning a metal chalcogenide residue from a deposition chamber surface.Deposition system 100 can include deposition chamber 110 having interiorsurface 111, deposition gas inlet 121, reactive gas inlet 131, inert gasinlet 141, and outlet 170. Deposition gas source 120 can be connected todeposition gas inlet 121 and configured to deliver a deposition gas todeposition chamber 110. Reactive gas source 130 can be connected toreactive gas inlet 131 and configured to deliver a reactive gas todeposition chamber 110. The reactive gas can react with a metalchalcogenide formed on interior surface 111 to form a purgable material.Inert gas source 140 can be connected to inert gas inlet 141 andconfigured to deliver an inert gas to deposition chamber 110 and flush apurgable material from deposition chamber 110 through outlet 170.

Deposition system 100 can include conveyor 150 to transport substrate200 into and out of deposition chamber 110. Loadlock 160 can beinstalled at the both ends of conveyor 150 to control the deposition andcleaning process.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Itshould also be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention.

1. A method of cleaning a deposition chamber comprising: pulsing areactive gas comprising a hydrogen halide into a deposition chambercontaining a metal chalcogenide formed on a deposition chamber surfaceto form a purgable material; and purging the purgable material from thedeposition chamber.
 2. The method of claim 1, wherein the purgablematerial includes a vapor or a particulate.
 3. The method of claim 1,wherein the hydrogen halide comprises hydrogen chloride.
 4. The methodof claim 1, wherein purging the purgable material from the depositionchamber comprises pulsing an inert gas into the deposition chamber toflush the purgable material out of the chamber.
 5. The method of claim2, further comprising heating the deposition chamber to maintain thepurgable vapor material as a vapor.
 6. The method of claim 1, furthercomprising introducing a chemically reactive plasma into the depositionchamber to react with metal chalcogenide.
 7. The method of claim 1,further comprising pulsing a second reactive gas into the depositionchamber after pulsing the reactive gas into the deposition chamber. 8.The method of claim 7, wherein the second reactive gas comprises anacid, oxygen, fluorine, or tetrafluoromethane
 9. The method of claim 4,wherein the inert gas comprises helium or nitrogen.
 10. A method ofmanufacturing a semiconductor device, comprising: transporting asubstrate into a deposition chamber; forming a buffer layer adjacent tothe substrate, wherein forming the buffer layer comprises pulsing atleast one metal precursor and pulsing at least one chalcogen precursorinto the chamber; transporting the substrate with the deposited bufferlayer out of the chamber; and pulsing a reactive gas comprising ahydrogen halide into the deposition chamber to react with a metalchalcogenide formed on a deposition chamber surface to form a purgablematerial; and purging the purgable material from the deposition chamber.11. The method of claim 10, wherein the purgable material comprises avapor or a particulate.
 12. The method of claim 10, wherein the hydrogenhalide comprises hydrogen chloride.
 13. The method of claim 10, whereinpurging the purgable material from the deposition chamber comprisespulsing an inert gas into the deposition chamber to flush the purgablematerial out of the chamber.
 14. The method of claim 11, furthercomprising heating the deposition chamber to maintain the purgable vapormaterial as a vapor.
 15. The method of claim 10, further comprisingpulsing a second reactive gas into the deposition chamber after pulsingthe reactive gas, wherein the second reactive gas comprises a materialselected from the group consisting of an acid, oxygen, fluorine, andtetrafluoromethane.
 16. The method of claim 10, wherein the inert gascomprises a material selected from the group consisting of helium andnitrogen.
 17. The method of claim 10, further comprising heating thesubstrate before pulsing a precursor.
 18. The method of claim 10,further comprising forming a chemically reactive plasma in thedeposition chamber to react with the metal chalcogenide.
 19. The methodof claim 10, wherein the semiconductor device comprises a photovoltaicdevice.
 20. A system for cleaning a metal chalcogenide residue from adeposition chamber surface, comprising: a deposition chamber comprisingan interior surface, a deposition gas inlet, a reactive gas inlet, aninert gas inlet, and an outlet; a reactive gas source connected to thereactive gas inlet and configured to deliver a reactive gas comprising ahydrogen halide to the deposition chamber, where the reactive gas canreact with a metal chalcogenide formed on the interior surface to form apurgable material; an inert gas source connected to the inert gas inletand configured to deliver an inert gas to the deposition chamber andflush a purgable material from the deposition chamber through theoutlet.
 21. The system of claim 20, wherein the metal chalcogenidecomprises a material selected from the group consisting of aluminum,titanium, indium, and zinc.
 22. The system of claim 20, wherein themetal chalcogenide comprises a material selected from the groupconsisting of oxygen, sulfur, and selenium.
 23. The system of claim 20,wherein the hydrogen halide comprises hydrogen chloride.
 24. The systemof claim 20, further comprising a second reactive gas source comprisinga second reactive gas comprising a material selected from the groupconsisting of an acid, oxygen, fluorine, and tetrafluoromethane.
 25. Thesystem of claim 20, wherein the inert gas source comprises a materialselected from the group consisting of nitrogen and helium.
 26. Thesystem of claim 20, further comprising a heater to heat the depositionchamber interior surface to a temperature sufficient to maintain apurgable material as a vapor.